I've seen the stats, and those problems didn't start to show up in the black community until the 1940's.
They started to show up in the wider community about 20 years later.
The welfare requirement of no working male in the household was what did it. That was a systematic defect of the welfare system that was an organic inheritance from Jewish welfare practice of direct cash payments to widows in need, which liberal welfare policies copied for obvious reasons. The liberals who grafted these policies onto a secular program didn't stop to think that the strong social and moral controls in the Jewish community and the strong moral leadership exerted by the rabbinate and Jewish womanhood's moral upbringing might be lacking in the wider community, with large consequences. This failure to anticipate the workings of Murphy's Law -- this failure to consult conservative wisdom, frankly -- was what doomed the welfare concept and the programs founded on it.
We have a winner! When you subsidize poverty you will get more poverty. The real question is why the Democrats never try to fix it and always block Republican attempts to fix it.